1. Field of the Invention
The present invention relates to a liquid application device and an inkjet recording apparatus, and particularly to a liquid application device for applying liquid to a medium for a certain purpose which is, for example, to promote the coagulation of pigment when recording is carried out using an ink which contains the pigment as a coloring material. The present invention also relates particularly to an inkjet recording apparatus which includes a mechanism for applying liquid to a recording medium used in inkjet recording, for a purpose which is, for example, to promote the coagulation of pigment when recording is carried out using an ink containing the pigment as a coloring material.
2. Description of the Related Art
In the field of printing, there has been conventionally known a gravure printing machine having a configuration where an area in which ink as application liquid is applied or supplied to a roller having a print pattern of a printing plate formed on a surface thereof (Japanese Patent Application Laid-open No. Hei 08-58069 A), is sealed off. In this machine, an ink chamber having two doctor blades is caused to abut the circumferential surface of the roller, thereby forming an ink room (an ink reservoir) between the chamber and the roller.
Additionally, means for supplying application liquid to an application mechanism of application liquid using a closed space as is disclosed in Japanese Patent Application Laid-open No. Hei 08-58069 A, is disclosed in Japanese Patent Application Laid-open No. Hei 06-246902 A. In Japanese Patent Application Laid-open No. Hei 06-246902 A, the application liquid is circulated by using a pump in a circuit where an application mechanism, and application liquid storage means which stores the application liquid are connected via two channels. In the configuration of this document, the above pump is arranged downstream of the application mechanism (in the collection channel of the channels connecting the application mechanism and the application liquid storage means). With this configuration, the internal pressure in the application mechanism keeps not higher than the atmospheric pressure, whereby liquid leakage in the application mechanism can be prevented. Furthermore, in the configuration of the same document, a valve, used for switching communication with the atmosphere and communication with the application liquid storage means, is arranged upstream of the application mechanism in the circuit for the circulation. With this valve, it is made possible to collect the application liquid inside the application mechanism. This collection operation makes possible the prevention of the application liquid leakage which may occur when a device, not in use, including the application mechanism is carried around.
On the other hand, in the field of inkjet recording, there has been known, as one configuration for supplying ink to a recording head, a configuration where first liquid storage means (a buffer tank) and second liquid storage means (a main tank) are provided (Japanese Patent Application Laid-open No. 2001-232807 A). In this configuration, the first liquid storage means (the buffer tank) is provided in a circulation supply path, and the second liquid storage means (the main tank) is linked with this first liquid storage means. This configuration using the buffer tank makes it possible to maintain a pressure in the recording head at a constant level in consideration of stable supply of the ink. That is, in the configuration of Japanese Patent Application Laid-open No. 2001-232807 A, fluctuation in pressure in the recording head is suppressed by reducing a difference in water head between a liquid surface of the ink inside the buffer tank, and the recording head for the purpose of stabilizing the applied amount of the ink.
In the configuration of Japanese Patent Application Laid-open No. 2001-232807 A, since the two above-mentioned liquid storage means, and the printing head are included, there exist two routes for supplying the ink to predetermined members, and one pump is provided to each of the two routes. Out of these pumps, a first pump is provided between the recording head and the buffer tank, and performs supply of the ink from the buffer tank to the printing head. On the other hand, a second pump is provided between the buffer tank and the main tank, and performs supply of the ink from the main tank to the buffer tank.
In a recording apparatus described in Japanese Patent Application Laid-open No. 2001-232807 A, the buffer tank and the main tank are provided for the purpose of deaeration. By this means, intrusion of air bubbles into the recording head is reduced when the ink is supplied to the recording head. Furthermore, it is also desirable that the buffer tank be provided in view of the stabilization of the application amount of the ink, as has been described above.
In Japanese Patent Application Laid-open No. 2001-232807 A, however, the first pump for supplying the ink from the buffer tank to the printing head, and additionally, the second pump for supplying the ink from the main tank to the buffer tank, are necessary. In recent years, further miniaturization and cost reduction of the apparatus have been desired. For these purposes, in a liquid application device and a recording apparatus each of which includes two liquid storage means, it is preferable that the number of parts constituting each of the device and the apparatus be reduced, the parts including such as a pump, a channel and a control unit necessitated by the pump.